Remember that Zinc won't prevent colds, but may reduce the duration of symptoms:
http://www.aafp.org/afp/20010215/tips/7.html

I read that the form of zinc is important. I looked around and found that Rite-Aid brand zinc lozenges have zinc acetate.

I'm going to give Echinacea a try as well.

I agree the most with stimpy regarding the benefits of sleep. Stress and the lack of sleep suppress the immune system. I stop reading the newspaper and focus on mindless TV shows in between long periods of sleeping and napping when I have a cold!